Method of adding alloy additions in melting aluminum base alloys for ingot casting

Abstract

A method of adding alloying elements, including highly reactive metals suchs lithium, to molten aluminum so that the normally occurring oxidation reaction of such elements with the atmosphere is minimized. After adding all alloying elements, except the highly reactive metals, to the molten aluminum, and after the alloyed melt has been subjected to a degassing and filtering process, the reactive metals are introduced in a mixing crucible as the final step prior to the casting operation. The desired concentration of reactive metal in the melt is achieved by controlling the relative amounts of reactive metal and alloyed melt. Uniformity of the mixture is controlled by mechanical stirring. The alloyed metal is then cast into ingots.

What is claimed is: 
     
       1. The method of making an aluminum alloy containing aluminum and alloying elements including a highly reactive metallic element, comprising: establishing a bath of molten aluminum;   adding all alloying elements to said bath except said highly reactive metallic element, thereby establishing an alloy melt,   treating said alloy melt to remove hydrogen gases therefrom, and   combining said reactive metallic element with said treated alloy melt,   whereby the addition of said reactive metallic element to said melt after treating said melt ensures minimization of the oxidation rate of the melt.   
     
     
       2. The method as set forth in claim 1 wherein said step of treating includes degassing said alloy melt and said step of combining comprises: melting said highly reactive metallic element in a melting furnace, and   blending said reactive element melt with said treated alloy melt.   
     
     
       3. The method of claim 2 wherein said step of blending includes stirring said reactive element melt and said degassed alloy melt. 
     
     
       4. The method of claim 2 wherein said step of combining further includes metering a predetermined amount of said molten reactive element out of said melting furnace. 
     
     
       5. A method of combining aluminum with alloying elements comprising the steps of melting said aluminum, combining said aluminum with at least one alloying element to form an alloy melt, degassing said melt to substantially remove hydrogen therefrom, adding a quantity of a highly reactive metallic element to said substantially degassed alloy melt, and casting the melt. 
     
     
       6. The method of claim 5 wherein said step of introducing comprises melting said reactive element. 
     
     
       7. The method of claim 5 wherein said step of introducing further includes measuring out a portion of said melted reactive element for addition to said alloy melt. 
     
     
       8. The method of claim 6 wherein said step of introducing includes mixing said melted reactive element with said alloy melt. 
     
     
       9. The method of claim 8 wherein said step of mixing includes stirring said alloy melt as said melted reactive element is added thereto. 
     
     
       10. The method as set forth in claim 5 wherein the step of adding of a highly reactive metallic element comprises adding lithium. 
     
     
       11. A method for making an aluminum alloy containing aluminum and at least two metallic substances, at least one of said metallic substances being highly reactive which would significantly increase the oxidation rate of the alloy when in its molten form, at least one other of said metallic substances having a relatively low reactance with oxygen which would not significantly change the oxidation rate of the molten alloy when added to the aluminum, wherein the method comprises the steps of: melting said aluminum to form a melt;   adding said at least one other metallic substance to said melt;   degassing said melt to substantially remove any contaminating substance in gaseous form therefrom;   adding a measured quantity of melted highly reactive metallic substance to said melt while treating said melt and mixing said melt to substantially blend said highly reactive metallic substance with said melt;   casting said melt.   
     
     
       12. The method as set forth in claim 11 wherein the step of degassing comprises degassing to substantially remove hydrogen. 
     
     
       13. The method as set forth in claim 11 or 12 wherein the at least one other of said metallic substances is selected from a group consisting of Fe, Ni, Co, Mn, Nb, Ti, Zr, Hf, W, Cr, Mo, and Si. 
     
     
       14. The method as set forth in claim 13 wherein the at least one highly reactive metallic substance includes lithium. 
     
     
       15. The method as set forth in claim 14 wherein the step of degassing said melt includes degassing said melt in a holding furnace, and the step of adding a measured quantity of said highly reactive substance includes melting said highly reactive substance in a melting crucible and measuring said highly reactive substance in a measuring crucible which is substantially enclosed and has an inert atmosphere; and the step of mixing the melt includes mixing said highly reactive substance with said melt in an alloy mixing crucible which is substantially enclosed and has an inert gas atmosphere. 
     
     
       16. The method as set forth in claim 14 wherein the treating of said melt after the lithium has been added includes bubbling inert gas through the melt to remove dissolved gases and high pressure contaminates.